The present invention relates to a system for cooling components which in use, experience high temperatures. The invention has particular efficacy in the gas turbine field, and may be incorporated in gas turbine engines of the kinds used to power aircraft or ships, or to pump oil overland.
Air impingement cooling of gas turbine engine combustion equipment and other structures therein, is well known. However, known systems, wherein cooling air flowing over the surface of one member, passes through holes and crosses a gap, to impinge on a surface of an adjacent hot member, fail to achieve their full cooling potential. This is because the jet of air, on striking the surface of the hot member, spreads over the surface, effectively in a layer of constant thickness. It follows, that the outer portion of the layer never touches the hot member, and consequently, cannot make an efficient contribution to the cooling effect of the air flow.
A further drawback to known impingement cooling systems, is that, having impinged on the hot surface, and spread through 360xc2x0 over the hot surface, the respective air flows collide with each other, and form a turbulent mix with poor heat transfer performance, and which sometimes displaces incoming air jets. Hot spots are thus formed.
The present invention seeks to provide an improved air impingement cooling system.
According to the present invention, an air impingement cooling system comprises superimposed, spaced apart members, one perforated, the other having a surface portion directly under each respective perforation, each said surface portion being of fluctuating shape, so as to cause air received thereby via respective perforations, and deflected laterally there across, to flow over said fluctuations, said fluctuating shape being such that the boundary layer of said air flow over said surface portion is caused to separate from said surface portion in the region of said fluctuations and subsequently reform downstream of said separation.